@vbs Hello Vincent....
If you upload your patch to the forum it helps us understand your problems better, but I think maybe what you need is quite simple........
and use the bang to send the message. What osc message is sent? Do you send the velocity value? or the Note value? Or?
David.

I have don this and it works aldo i don't understand the select part if i leave this out it works as well.
No the problem is that it jumps two page instead of one, because it is reacting to on velocity 127 and of velocity 0.

I have now change the note to 52 to degrees the page and 53 to increase.

I upload it this time so maybe you have a look at this what to to to make only react to velocity 127

@vbs Hello VBS........ I don't have any midi at the moment to test, but try this........
I don't know if the note or the velocity arrives first....... probably the note..... but these "expr" objects are saying "if the note = x and the velocity = 127 then send a 1.... if not a 0.velocity.pd
There is a problem that if the note arrives before the velocity then the note is "passed" before the velocity changes to 0
Try this........velocity2.pd
The spigot opens with the desired note, and only a velocity of 127 will bang the message.....
or, using [expr] again......velocity3.pd
and...
.......there is an object designed to strip 0 velocity messages...... [stripnote] which does very simply as you want to do!...... sorry, I should have remembered that!
David.